Anyone who understands and can explain

1.)of the structures shown below, which is a constitutional isomer of n-pentane?

3.)which of the following statements about intermolecular forces is true?

the large london dispersion forces between helium atoms make helium difficult to liquefy.
intermolecular forces in a liquid are weaker than intramolecular forces.
ion–ion forces in an ionic solution are independent of the distances between ions.
dipole–dipole forces dominate in interactions between carbon dioxide molecules.

4.)elementary phosphorus is a solid consisting of p4 molecules and melts at 44 °c. the principal forces between the molecules in the solid must be

london dispersion.
ionic.
covalent.
dipolar.
metallic.

van der waals forces account for the cohesive energy of an ionic liquid.